The present invention relates to an inspection device for an ion implanter, and in particular, to an inspection device for examining a piece of aperture graphite of an extraction electrode of an ion implanter.
Recently, the ion implanting technology has been well developed. The recently available ion implanting technology not only satisfies needs for various semiconductor doping processes, but also becomes the most essential doping technology in the process for fabricating very large semiconductor integrated circuits.
An ion implanter is an apparatus for carrying out the ion implanting technology, including an ion source system for generating ions, a mass analyzer for separating major doped ions, and an accelerator for accelerating the ions to be implanted. The ion source system includes an evaporator, an arc chamber, a magnet, and an extraction electrode. The detailed description of the arc chamber and extraction electrode will be made in the following.
Referring to FIG. 1, plasma 3 is produced by the ion source (not shown) accommodated in an arc chamber 1 having an outlet 11. An extraction electrode 2 includes a suppression electrode 21, a ground electrode 22, and an insulator 23. The suppression electrode 21 includes two suppression electrode plates 211 and two suppression electrode aperture graphite elements 212. The ground electrode 22 includes two ground electrode plates 221 and two ground electrode aperture graphite elements 222. The suppression electrode 21 is provided with a suppression voltage SV, and the ground electrode 22 is grounded.
A suppression electrode aperture 213 is formed between the two suppression electrode plates 211 and between the two suppression electrode aperture graphite elements 212. A ground electrode aperture 223 is formed between the two ground electrode plates 221 and between the two ground electrode aperture graphite elements 222.
The ion beam from the arc chamber 1 is attracted out via the outlet 11 by the extraction electrode 2. The ion beam attracted out passes through the suppression electrode aperture 213 and the ground electrode aperture 223 while being focused for the next treatment.
Referring to FIGS. 2 and 1, the extraction electrode 2 includes a suppression electrode 21 and a ground electrode 22. The suppression electrode 21 includes two suppression electrode plates 211 and two suppression electrode aperture graphite elements 212. The ground electrode 22 includes two ground electrode plates 221 (not shown) and two ground electrode aperture graphite elements 222 (not shown). The construction of the ground electrode 22 and that of the suppression electrode 21 are substantially similar to each other.
Referring to FIG. 3A, each of the suppression electrode aperture graphite elements 212 includes a first to-be-examined curve 2121, two first engagement surfaces 2122, two second engagement surfaces 2123, and a first lower surface 2124. Referring to FIG. 3B, each of the ground electrode aperture graphite elements 222 includes a second to-be-examined curve 2221, two third engagement surfaces 2222, and a second lower surface 2223.
Referring again to FIG. 1, the extraction electrode 2 is used for attracting the ion beam from the arc chamber 1 in order to produce an ion beam current. Then, the ion beam current is focused. The suppression electrode aperture graphite elements 212 and the ground electrode aperture graphite elements 222 are those in contact with the ion beam current.
The curvatures of the arc surfaces of each of the suppression electrode aperture graphite elements 212 and each of the ground electrode aperture graphite elements 222 influence the diffraction of the ion beam current passing through the suppression electrode aperture 213 and the ground electrode aperture 223, and also influence the focusing of the ion beam current. The degrees of the influences can be examined during the tuning process of the ion beam, with reference to the variation of the suppression voltage SV.
In the extraction electrode 2, the suppression electrode aperture graphite elements 212 and the ground electrode aperture graphite elements 222 are considered as consumables. After they are utilized for some time, the first to-be-examined curve 2121 and the second to-be-examined curve 2221 are easily deformed and this can affect the ability of tuning ions of the ion implanter. In this case, the ion beam current does not reach a normal value, and the suppression voltage SV has to be increased in order to increase the focusing ability. According to this method, some electric power is wasted and other elements (not shown) within the extraction electrode 2 can be damaged in a short period of time.
In addition, if the deformation of the arc surface of the ground electrode aperture graphite element 222 and that of the suppression electrode aperture graphite element 212 have to be examined before each operating process, the steps of mounting a plurality of elements, vacuuming, tuning the ion beam, and the like are needed. Thus, a high manufacturing cost will be incurred.
In accordance with the first aspect of the invention, an inspection device for examining a piece of aperture graphite of an extraction electrode is disclosed. The aperture graphite has a to-be-examined curve and a to-be-examined engagement portion. The inspection device comprises a sidewall surface having a standard curve marked thereon, and an examination engagement portion having a predetermined positional relationship with the sidewall surface while the to-be-examined engagement portion is engaged with the examination engagement portion and the to-be-examined curve is projected onto the sidewall surface. The suitability of the aperture graphite can be determined according to the amount of difference between the projected to-be-examined curve and the standard curve.
The amount of difference between the projected to-be-examined curve and the standard curve comprises area difference that is the difference between the area enclosed by the projected to-be-examined curve and that by the standard curve, and maximum distance difference that is the maximum distance difference between the projected to-be-examined curve and the standard curve.
The aperture graphite is determined as unsuitable when the maximum distance difference is larger than 0.5 mm.